Firefox Quantum using 1GB of RAM with only two tabs open. (Version 57.0)

I originally tried the Beta for Firefox Quantum, and, it used a bit of my RAM to just keep open. While three tabs were open, it was using about 1.2GB of my RAM.

I ended up getting the actual release for it and it's doing the exact same thing. According to my friend, it only uses about 100MB with only one tab open. While for me, when I open ONE tab. It blasts up to 500MB.

Most of the used RAM is probably cache, including preallocated (a.k.a. just reserved, not actually used). That means if other programs use more than 50% of your total RAM Firefox will release some (you can test this by starting a few games simultaneously or removing/disabling some of your RAM). It also depends on what pages you have open - for example Reddit will use far less memory than Facebook. An adblocker will save you some resources as well. Using more RAM isn't a bad thing, it means less disk usage (stuff is cached in disk if not in RAM). The memory information per process is in about:performance.